Feel like an idiot: Contractions vs. tightness--STM

Spacebunny19

So on Monday I was having a buncha contractions, got in to see my OB and was given the all clear (yes I'm 1 cm dilated and she's fully dropped/head down rarin' to go).  But, although she explained that since I'm a STM, and I'm also HUGE (or so I think) there is a lot of tightness I'm experiencing that is not contraction.  I was even experiencing what I thought was a contraction during my exam and she said my abdomen was NOT tightening for a contraction at that point--but to me it felt like it was.

So, since then I have been really trying to pay attention to my body and figure out when I'm having a BH or contraction of any sort vs. just the tightness, and I am having the darnedest time doing it, and so I feel like an IDIOT.   

Is anyone else experiencing this?  Why would tightness of that extreme nature (where i could seriously bounce a quarter off my belly)  which comes & goes--just like a contraction--but *isn't* a contraction?  

Now I'm half afraid that I'll be in labor and dismiss it until it gets way intense because it's just *tightness* in my head.  (FWIW when I was in labor with DD#1 my contractions were the right timed apart but not all that intense when it started, but so close together I did go in right away and had her that day, so the whole "if you can talk through it" rule didn't even apply then. The contractions didn't get crazy painful (thank you back labor sunny side up baby) until about 6 hours into labor.